Difference in self-fertilization efficiency among three loquat cultivars.
Loquat (Eriobotrya japonica, Rosaceae) carries the gametophytic self-incompatibility (GSI) fertilization system. In a recent work we found that the commercial loquat cultivars 'Yehuda', 'Akko 1' and 'Avri' share the S6-allele, but differ in the other S-allele. Analysis of the progeny showed that the three cultivars are self-compatible, and PCR analysis suggested that the S6 haplotype is responsible for the breakdown of GSI. Nevertheless, in a mixed cultivar orchard, self-fertilization levels differed between the three cultivars: 95% in 'Yehuda', 84% in 'Akko 1' and 77% in 'Avri'. We suspected that the difference among cultivars was due to the flower properties related to pollination and therefore the following parameters were examined along the flowering season: (a) in vitro pollen viability, (b) in vitro pollen viability at different temperatures, (c) percentage of flowers with viable pollen, and (d) germination levels of pollen in the stigmas. 'Yehuda' scored highest for all parameters tested, and it was therefore concluded that its high level of self-fertilization is due to its superior flower properties. However, the effective self-fertilization of 'Yehuda' did not result in higher seed set.